Intra-Osseous Implant

ABSTRACT

The invention relates to an intra-osseous implant for placement in bone of a human or animal body, which allows an accurate implant position at a desired depth into bone tissue, providing without losing a high degree of primary implant stability, comprising at least one intra-osseous part intended for placement in said bone tissue having an apical side and a cervical side, which part is provided on its circumferential surface with a thread running in the direction of the apical end and with one or more grooves extending in longitudinal direction and interrupting the screw thread into multiple interrupted screw thread parts serving as retention elements allowing the placement of the implant in longitudinal direction into said bone tissue but preventing the removal of the implant in opposite longitudinal direction of said bone and a support part present at said cervical side of said at least one intra-osseous part intended for supporting a prosthetic element.

The invention relates to an intra-osseous implant for placement in boneof a human or animal body comprising at least

one intra-osseous part intended for placement in said bone tissue havingan apical side and a cervical side and composed of a body friendlymaterial, which part is provided on its circumferential surface with athread running in the direction of the apical end; and

a support part present at said cervical side of said at least oneintra-osseous part intended for supporting a prosthetic element.

Present intra-osseous implants are frequently used for medical purposes,such as (hip-, knee- and finger-) joint prostheses and bone screws fortraumatology. Also these intra-osseous implants are used as dentalimplants in dentistry and oral and maxillofacial surgery.

An important development in dentistry and oral and maxillofacial surgeryin the last two decades, is the application of dental implants. These‘artificial’ tooth roots are used to replace lost natural teeth andgenitally absent teeth. Upon these implants removable overdentures orfixed crowns or bridges can be placed.

Dental implants can be placed in the bone after implant bed preparationwith one or more drills. After a certain integration period they can beloaded, for example by chewing. The prosthetic parts will provide thepatients with essential functions like chewing ability, speech,appearance and self-esteem.

Most dental implants are rotation symmetric, the majority having a screwthread design.

Usually the threaded dental implants excludes an asymmetric implantdesign (e.g. angled or bevelled or scalloped), since the criticalposition of the implant clashes with the intended implant placementdepth. Although the screw thread provides the implant of a goodretention, it limits on the other hand the depth accuracy of the placedimplant.

The pitch of the screw thread defines the depth positioning of animplant. A large pitch allows a quick insertion procedure, but the depthpositioning towards the surrounding bone and the next structures is lessaccurate. On the other hand a screw thread having a small pitch allowsan accurate implant position, but offers less primary implant stabilityand a time consuming surgical procedure.

Rotation asymmetric implants benefit in this respect from a cylinderdesign, since the implant is tapped or pushed into its desired position,after the implant bed is prepared the appropriate drills. This is a veryfast surgical procedure. However the retention of the implant towardsthe surrounding bone is limited, especially if the bone is of anon-dense (weak or loose) structure.

In other words the cylindrical implants have a better position abilitythan screw implants, but the primary stability is lower. Thisobservation is not only applicable for implant dentistry, but also formedical indications.

With respect to the above mentioned, the invention aims to provide amedical intra-osseous implant and especially a dental intra-osseousimplant, which allows an accurate implant position at a desired depthinto bone tissue, providing without losing a high degree of primaryimplant stability. Also the proposed implant design will allow a shortsurgical procedure with an improved suture of bone tissue to the implantas well as providing an intra-osseous implant having a stronganti-rotation characteristic.

According to the invention the intra-osseous implant is characterized inthat the intra-osseous part is provided with one or more groovesextending in longitudinal direction and interrupting the screw threadinto multiple interrupted screw thread parts, said multiple interruptedscrew thread parts serving as retention elements allowing the placementof the implant in longitudinal direction into said bone tissue butpreventing the removal of the implant in opposite longitudinal directionout of said bone.

The presence of one or more groove-like interruptions of the screwthread allows a quick and accurate placement of the implant into thebone, without the necessity to screw the implant into its properposition. The implant can merely be tapped or pushed into its properposition significantly reducing the time of the surgical procedure.

The remaining thread parts on the intra-osseous implant surface functionas retention elements (like shark teeth) exerting vertical androtational retention forces on the surrounding bone tissue. This ensuresa proper primary implant stability of the intra-osseous implantaccording to the invention.

However the remaining thread parts (retention elements) still form a(though interrupted) screw thread, so that the implant can also be(re)positioned by means of screw (rotation) action. The interruptedscrew thread also allows removal of an implant that has just beeninserted, but intra-operatively regarded as not properly positioned.

The implant invention combines the advantages of a fast surgicalprocedure and an accurate placement and positioning of the intra-osseousimplant. Also it provides the implant of a good primary stability and ahigh retention against vertical and rotational forces.

In a specific example of the invented implant the groove extends overthe entire length of the intra-osseous part of the implant, wherein thedepth of the groove can be smaller, equal or greater than the height ofthe screw thread.

More in particular the width of the groove varies in the direction ofthe apical side of said intra-osseous part and more in particularwidens. Also the depth of the groove may vary in the direction of theapical side of said intra-osseous part and more in particular becomeslarger, or the height of the screw thread may vary in the direction ofthe apical side of said intra-osseous part and more in particularbecomes smaller.

In specific and favourable designs of medical or dental (or veterinary)bone implants according to the invention the intra-osseous partcomprises multiple grooves.

A better stability of the implant according to the invention is acquireddue to the longitudinal grooves, which are present in an equidistantmanner in the surface of the intra-osseous part of the implant.

With an advantageous embodiment the insertion of the implant into thebone is facilitated and speed as according to the invention theintra-osseous part has a cylindrical cross section. However in otherembodiment the intra-osseous part may have a near cylindrical crosssection, for example a conical, elipsonal, oval cross section.

More in particular the intra-osseous part may exhibit a polygonal crosssection, for example a pentagon or hexagonal or heptagon or octagonalcross section.

A further improved insertion of the implant according to the inventionis obtained as the intra-osseous part becomes smaller in the apicaldirection.

In specific implant designs the intra-osseous part of the implant mayhave a conical shape or be narrower towards the apex of the implant.

In another embodiment the support part is positioned under an angle onsaid intra-osseous part with respect to the direction of implant.

In another specific design the intra-osseous implant is intended as adental implant, where the shape is adapted to the shape of the alveolarcrest. Unlike most dental implants available at present, the shoulder ofthe implant, that is the circumferential edge of the support (orconnection) part will not be rotation symmetric. It may for example bescalloped, bevelled, curved or angled to accommodate the bony contoursof the jawbone. In this manner the implant shape will allow properaesthetics in the regions of aesthetic relevance (mainly the frontalteeth in the upper jaw).

The shape of the natural tooth is such that the crown on the buccal(lip- or cheek- or out-) side (and palatal or oral side), extendsfurther to the apex (towards the end of the implant) than on theinterproximal sides. In most dental implants the rotation symmetricdesign of the implant does not allow a crown margin that follows thesecontours. The result is that the crown is buccally not deep enough andinterproximally too deep in to the tissues. The first aspect is negativefor the aesthetic appearance (it is less beautiful, sometimes showingimplant metal). The second may impair the hygienic possibilities and maylead to peri-implant bone loss.

The disadvantages of the above mentioned conventional dental implantscan be dealt with by creating a bevel (concave excavation or flattening)on one side (meant to be placed on the buccal side of the jaw) of theimplant. In this case the above-mentioned problems of a too deep placedimplant shoulder (=crown margin) on the interproximal sides and a notdeep enough placed implant shoulder (=crown margin) on the buccal side,can be dealt with.

The present dental implants are usually of a straight design. The shapeof a natural tooth shows a small angle between the root and the crown ofthe tooth, in a specific embodiment the support part is positioned underan angle on said intra-osseous part with respect to the direction ofimplant. The implant invention allows the implant to be of an angleddesign, thus dealing with anatomical requirements of the jaws and teeth.

The invention will be described with reference to a drawing, whichdrawing shows in:

FIG. 1 a-1 c several embodiments of an intra-osseous implants accordingto the state of the art;

FIG. 2 a first embodiment of an intra-osseous implant according to theinvention;

FIGS. 3-10 more embodiments of an intra-osseous implant according to theinvention.

The following description of the Figures describe several embodiments ofintra-osseous implant designs, which are meant to be used as dentalimplants. However the invention is, depending on the indication andmedical application as well as the surgical treatment, not limited toonly dental implant, but also applicable to other bone implants or bonescrews or bone nails.

FIGS. 1 a-1 c disclose conventional dental implants 1 according to thestate of the art having an elongated shape and manufactured of a tissuefriendly material, such as titanium or a titanium alloy. The implant 1has a root part also called an intra-osseous part 2, which is meant tobe placed in an implant bed preparation 3 in the jaw bone 4.

The intra-osseous implant 1 also has a support connection or mountingpart 5, which usually is utilised to insert the implant with. Thesupport part 5 is also used to support and mount or connect theprosthetic device 6 (supra-structure, e.g. crown, bridge or overdenture) at a later stage.

An essential factor in implant dentistry is the accurate depth of theintra-osseous implant 1 into the bone 4 during placement. An accuratedepth in implant placement has a significant aesthetic relevance, but isalso of importance for a good oral hygiene and peri-implant health.Disregarding the rules of the biologic width (in the event an implant isplaced too deeply) will lead to bone loss. On the other hand, if theimplant is not placed deeply enough, the aesthetic result will bedisappointing (visible crown margin or implant shoulder).

An accurate placement of implants can be achieved by using cylindricalimplants as shown in FIGS. 1 a and 1 b. Such cylindrical implants 1allow a quick and accurate placement of the implant into the bone 4, butthe cylindrically shaped intra-osseous part 2 provides a less primarystability in the implant bed preparation 3 than with a screw implant.

In order to increase the bone contact between the circumferentialsurface 2 a of the intra-osseous part 2 and the bone tissue wall of theimplant bed preparation 3 and therefore to improve the implant stabilityin the jaw bone 4, a well-known intra-osseous implant 1 b has anintra-osseous part 2 with a hollow cylinder design provided with lateralperforations 7 to increase ingrowth of bone tissue.

Another well known implant design 1 c shows an intra-osseous part 2 witha screw thread 8 provided in its circumferential surface 2 a. The screwthread 8 provides the implant 1 with a high primary stability at implantplacement. It also guarantees an increased implant-bone contact surfaceand allows the implant to be loaded (e.g. by chewing) at an earlierstage after the implant procedure.

A disadvantage of a screw thread 8 present in the circumferentialsurface 2 a of the intra-osseous part 2 of the implant 1 is that thelimited accuracy in depth positioning is limited even if the implant isnot rotation symmetric (scalloped or bevelled or angled).

A screw thread 8 with a large pitch will permit a quick implantplacement, but involves minor accuracy as to the depth positioning ofthe implant with respect to the surrounding bone tissue. A screw thread8 with a smaller pitch allows a more accurate depth positioning, howeversuch design requires in turn a more time consuming surgery procedure andin extreme cases less primary stability of the implant due to thesmaller thread.

The invention aims to avoid above mentioned drawbacks and design animplant that allows a swift and accurate implant placement, providing ahigh degree of (primary) implant stability.

The intra-osseous implant 10 as shown in FIG. 2 according to theinvention consists of an elongated intra-osseous part 12 of a tissuefriendly material and a support or connection part 15 intended forimplant insertion and acting as a support or mounting area for aprosthetic device 6 (a supra-structure, e.g. crown, bridge or overdenture) at a later stage.

The intra-osseous part 12 of the implant 10 carries on its surface 12 aa screw thread 18 with a certain pitch.

According to the invention, the intra-osseous part 12 as shown in FIG. 2has on its circumferential surface 12 a a screw thread 18, which thread18 is interrupted by one or more longitudinal extending grooves 19 a-19c. The presence of one or more grooves 19 a-19 c results in a screwthread 18, which is composed of several sections 18 a-18 d depending onthe number of grooves 19 a-19 c.

More in particular these grooves 19 a-19 c etc. are present in anequidistant manner in the surface 12 a of the intra-osseous part 12 ofthe implant 10. Furthermore the intra-osseous part 12 of the implant maypreferably have a cylindrical cross-section. However also nearcylindrical cross-sections, like an elliptical, oval or conicalcross-section are possible.

More in particular the intra-osseous implant according to the inventionmay have a polygonal cross-section, for example a squar or pentagonal orhexagonal or heptagonal or octagonal cross-section.

Also combinations of one or more of the above embodiments are possible.

As a result of the configuration of the interrupted screw thread 18, theintra-osseous implant 10 according to the invention is not only a screwimplant, but can also be used as a cylinder implant. The cylindricalground form allows a swift surgical procedure, since the screw action isnot necessary. After placement of the implant 10 at the desired positionand depth into the bone 14, the screw parts 18 a-18 c etc. present onthe circumferential surface 12 a of the intra-osseous part 12 act asretention elements positioned side-by-side in a longitudinal manner.

These retention elements function like shark teeth hooking on to thebone tissue 13 surrounding the implanted intra-osseous part 12. Withthese retention elements the implant 10 will have a good primarystability and a high retention against vertical and rotational forces.

Due to the fact that the retention elements 18 a-18 c etc. are situatedon adjacent rows orientated parallel to the implant axis, no undesiredturning or rotation of the intra-osseous implant 10 during implantinsertion into the implant preparation bed 13 will occur. Instead, theinsertion of the implant 10 simply by pushing or tapping it into itsdesired place, will guarantee a proper orientation and position withrespect to the surrounding (bone) tissue.

If so desired a symmetric or non-symmetric implant 10 can be properly(re)positioned in height (or depth) by turning the implant 10 in a screwmotion. Although interrupted by the longitudinal grooves 19 a-19 c etc.the interrupted screw thread parts 18 a-18 c etc. still function as acomplete thread with a certain pitch, thus allowing to alter the desiredinsertion depth and to maintain primary stability.

FIGS. 3 a and 3 b show detailed views of the embodiment shown in FIG. 2.The grooves 19 a-19 c etc. extend in longitudinal direction along thecircumferential surface 12 a of the intra-osseous part 12, in such amanner that the grooves 19 a-19 c more or less flatten the extendingedge 21 a-21 c etc. of the thread 18 a-18 c etc.

Each extended edge 21 a-21 c etc. of the thread 18 functions as aretention element towards the bone tissue 14 surrounding theintra-osseous part 12. A possibly wrongly inserted implant 10 can beremoved using the interrupted screw thread 18 a-18 c etc., by simplyunscrewing the implant using a proper and known tool after a certaininitial resistance has been surpassed.

In another embodiment as shown in FIG. 3 b each longitudinally extendinggroove 19 a-19 c etc is applied with a certain depth in thecircumferential surface 12 a of the intra-osseous part 12, whereby thethread 18 is locally completely removed.

The remains of the interrupted thread 18 in this design form severalrows 18 a-18 d etc. of thread parts, which encounter the surroundingbone as retention elements. This function guarantees a good stability ofthe implant in the (jaw-)bone, but also allows adjusting or removing awrongly placed implant. The retention elements 18 a-18 d etc exhibit asloping edge in the apical direction of the intra-osseous part 12allowing an uninterrupted insertion, but preventing the removal of theimplant by simply pulling. Removal is only possible by unscrewing theimplant out of the implant preparation bed 13 in bone 14.

Other designs of the intra-osseous implant according to the inventionare shown in FIGS. 4 a-4 d, 5 a-5 c and 6 a-6 b and 7, whereby thecorresponding elements of the different embodiments in the Figures areindicated with the same reference numerals.

The intra-osseous part 12 exhibits an apical end side 12 b, which entersthe implant preparation bed 13 first and a cervical or connection endside 12 c, which carries the support or connection part 15 intended forimplant insertion and acting as a support or mounting area for aprosthetic device 6 (a supra-structure, e.g. crown, bridge or overdenture). The surface 12 a shows a thread 18, which according to theinvention shows several longitudinal interruptions 19 a-19 c etc.

As described above, the interrupted thread parts 18 a-18 c etc. act likeretention elements placed on rows extending in longitudinal directionalong the circumferential surface 12 a of the intra-osseous part 12. Dueto their configuration these retention elements function like sharkteeth to hook into the surrounding bone tissue 14 as the profile of thethread exhibits a shallow slope towards the apical side 12 b and a steepor even rectangular slope on the cervical side 12 c. See also FIGS. 3 aand 3 b.

In FIG. 4 a an intra-osseous implant is shown having a conical ortapered form seen in the direction of the apex 12 b, while FIG. 4 bshows a cross section of a cylindrical form.

FIG. 4 c shows an embodiment with several grooves 19 a-19 c etc.extending over the entire longitudinal length of the intra-osseous part12 having a constant width B between the interrupted rows of screwthread parts (retention elements) 18 a-18 c etc., whilst the width B′ ofgrooves 19 a-19 c etc. increase towards the apex in the embodiment shownin FIG. 4 d. In FIG. 4 d the intra-osseous part 12 exhibit smallerretention elements at the apex 12 b than towards the cervix 12 c.

FIG. 5 a-5 c show further different embodiments of an intra-osseousimplant according to the invention, wherein the support or connectionpart (cervical part) 15 of the implant is positioned under an inclinedangle α with respect to the implant axis x of the intra-osseous part 12.The angle α between the axis of the support part 15 and the implant axisx of the intra-osseous part 12 may be in the range e.g. of 10°-20° andapproximately 15°.

The embodiments shown in FIGS. 5 b and 5 c disclose at least one bevel23 on the circumferential edge or shoulder 22 of the cervical (support)part 15 of the implant 10. In FIG. 5 b the bevel 23 shows a fluent orsmooth transition 24 from the shoulder 22 of the implant towards theapical side 12 b, whilst in FIG. 5 c the bevel 23 shows a clear andsharp transition angle 24.

As the transition 24 of the bevel 23 exhibits a convex shape in FIG. 5b, it will be apparent that also a concave transition 24 of the bevel 23is applicable.

More specifically, the implant according to this invention is placed insuch a manner that the bevel of the implant will be situated on thebuccal side, so that good aesthetics can be achieved.

FIGS. 6 a-b show combinations of embodiments of intra-osseous implantsalready described above and show two different combinations of a conicalimplant according to FIG. 4 a and a cylindrical implant according toFIG. 4 b. However also other combinations are possible e.g. a squar,pentagonal, hexagonal, heptagonal or octagonal design combined with acylindrical design.

FIG. 7 shows another embodiment of the intra-osseous implant accordingto the invention to be used in finger or toe joint surgery. The implant30 consists of two intra-osseous parts 31 a and 31 b and a joint 32. Theintra-osseous parts 31 a and 31 b are placed in the digits of thefingers or toes or other joints. Each intra-osseous part 31 a-31 b isprovided with a screw thread 18 resp. 18′. According to the inventionthe screw threads 18-18′ are interrupted by several grooves 19-19′. Aswas described above these interrupted thread parts 18-18′ act like sharkteeth, hooking into the surrounding bone.

Both intra-osseous parts 31 a-31 b can be introduced into the finger- ortoe-bone by simply using pressure or by tapping. Both intra-osseousparts 31 a-31 b are connected with a ball- or hinge-joint 32 or othertypes of joints or connections, in order to restore the normal finger-or toe-joint function.

FIGS. 8 a-8 e show several examples of different types and variations ofcross sections of the intra-osseous part 12 of the proposed implant 10according to the invention provided with grooves 19 interrupting thescrew thread 18.

In FIG. 8 a the grooves 19 show a round shape leaving sharp and pointingthread edges 18″, whilst FIG. 8 b shows flattened thread surfaces 18.FIG. 8 c shows a combination of narrow 19 and wider 19′ grooves. Thewide groove 19′ can be used to mark the position of the bevel 23 on thesupport part 15. This construction makes orientation during implantplacement more accurate and easy.

FIG. 8 d shows flat grooves 19 with sharp thread edges 18, whereas FIG.8 e shows trapezoid shaped thread profiles 18 due to a specific millingoperation.

The embodiment shown in FIG. 9 exhibits an intra-osseous part 12 with apolygonal ground form, for example a hexagonal cross-section. Howeveralso an octagonal or other polygonal shapes can be used as ground form.

Using a milling or machining operation a groove 40 is applied in thecircumferential surface of the intra-osseous part 12, said grooveextending in one or more (helical) windings 40 a-40 f along thecircumferential surface. Thus a screw thread 18 is created due to thismilling or machining operation having flattened parts 19 a-19 b etc. andextending retention elements 18 a-18 b etc.

Preferably the surface of the flattened parts 19 a-19 b coincide withthe surface of the groove windings 40 a-40 f.

The invention may also be applicable to another type of intra-osseousimplant: the “screw nail” or bone tack, which in fact exhibits aninterrupted screw thread as well. It can be used as a screw but also asa cylinder or as a nail (FIG. 10 a-10 b).

The embodiment of FIG. 10 a-10 b discloses an intra-osseous implant partshaped or configured as a nail.

The invention may be or may not be combined with other structures,formations or configurations of the implant.

The invention may concern the entire length of the implant or a part ofit.

1. An intra-osseous implant for placement in bone of a human or animalbody comprising at least one intra-osseous part intended for placementin said bone tissue having an apical side and a cervical side andcomposed of a body friendly material, which part is provided on itscircumferential surface with a screw thread running in the direction ofand ending at the apical end; and a support part present at saidcervical side of said at least one intra-osseous part intended forsupporting a prosthetic element, characterized in that the intra-osseouspart is provided with multiple grooves extending in longitudinaldirection and over the entire length of the intra-osseous part,interrupting the screw thread into multiple interrupted screw threadparts, said multiple interrupted screw thread parts serving as retentionelements allowing the placement of the implant in longitudinal directioninto said bone tissue but preventing the removal of the implant inopposite longitudinal direction out of said bone.
 2. (canceled)
 3. Anintra-osseous implant according to claim 1, characterized in that thedepth of the groove is smaller, equal or greater than the height of thescrew thread.
 4. An intra-osseous implant according to claim 1,characterized in that the width of the groove varies in the direction ofthe apical side of said intra-osseous part.
 5. An intra-osseous implantaccording to claim 1, characterized in that the depth of the groovevaries in the direction of the apical side of said intra-osseous partand more in particular becomes larger.
 6. An intra-osseous implantaccording to claim 1, characterized in that the height of the screwthread varies in the direction of the apical side of said intra-osseouspart and more in particular becomes smaller.
 7. (canceled)
 8. Anintra-osseous implant according to claim 1, characterized in that thegrooves are present in an equidistant manner in the circumferentialsurface.
 9. An intra-osseous implant according to claim 1, characterizedin that the intra-osseous part has a cylindrical cross section.
 10. Anintra-osseous implant according to claim 1, characterized in that theintra-osseous part has a near cylindrical cross section, for example aconical, elipsonal, oval cross section.
 11. An intra-osseous implantaccording to claim 1, characterized in that the intra-osseous part has apolygonal cross section.
 12. An intra-osseous implant according to claim1, characterized in that the intra-osseous part becomes smaller in theapical direction.
 13. An intra-osseous implant according to claim 1,characterized in that the support part is positioned under an angle onsaid intra-osseous part with respect to the direction of implant.
 14. Anintra-osseous implant according to claim 1, characterized in that theimplant is a dental implant, wherein said support part is provided withat least one bevel (flattening concavity) on its circumferential edge.15. An intra-osseous implant according to claim 4, characterized in thatthe width of the groove widens in the direction of the apical side ofsaid intra-osseous part.
 16. An intra-osseous implant according to claim11, characterized in that the intra-osseous part has a hexagonal crosssection.
 17. An intra-osseous implant according to claim 11,characterized in that the intra-osseous part has an octagonal crosssection.